The present invention relates to a circuit device according to the preamble of claim 1.
A circuit device of this general type is known from Valvo Report 79 04 23, "Technische Informationen fur die Industrie." The basic circuit shown and described there uses two multivibrators, wherein the durations of the square-wave pulses of one multivibrator are proportional to the capacity of a reference capacitor. Those square-wave pulses are used to synchronize the square-wave oscillations of the second multivibrator, the pulse duration of which is proportional to the capacity of the measuring sensor. The output signals of both multivibrators are connected in opposition so that a resulting pulse duration is achieved which corresponds to the difference between the pulse durations of both multivibrators.